Elastic wave device, method for manufacturing the same, and elastic wave apparatus

Abstract

The application relates to the technical field of elastic wave devices, in particular to a preparation method of an elastic wave device, which comprises the following steps: forming a photoresist structure on a partial region of a substrate; depositing an IDT metal layer on the substrate and the photoresist structure, the IDT metal layer having an extending foot; arranging a self-alignment layer on the surface of the IDT metal layer, the self-alignment layer not completely covering the extending foot; removing the extending foot and the photoresist structure which are not covered by the self-alignment layer; and forming a frequency modulation dielectric layer on the IDT metal layer and the substrate. By the arrangement, the extending foot of the IDT metal layer can be effectively removed, so that the prepared elastic wave device has excellent product characteristics.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of elastic wave devices, in particular to an elastic wave device and a preparation method thereof, and an elastic wave apparatus comprising the elastic wave device. BACKGROUND

[0002] The elastic wave device is a high-frequency filter with a passband frequency range of tens of MHz to several GHz. The elastic wave apparatus comprises a piezoelectric substrate, an interdigital transducer (IDT) electrode, i.e., an IDT metal layer, disposed on the upper surface of the piezoelectric substrate in the form of comb-shaped electrode fingers. Elastic waves are excited by applying a high-frequency electric field to the IDT metal layer from a lead terminal of a power supply side through a wiring pattern, and the elastic waves are converted into a high-frequency electric field through a piezoelectric effect, thereby obtaining the characteristics of the filter.

[0003] The morphology of the IDT metal layer is crucial for obtaining a filter with stable and excellent characteristics. Currently, the pattern forming process of the IDT metal layer mainly adopts a lift-off process. Since the IDT metal layer is formed by evaporation, there is inevitably a trailing phenomenon (commonly referred to as "footing" in English, which refers to the phenomenon that the bottom of the photoresist pattern is wide due to insufficient development in the photolithography process). The existence of the trailing phenomenon leads to the fact that the filter cannot obtain excellent K and Q values. The K value refers to the relationship between the conductivity of a semiconductor material and the temperature, and is usually used to describe the electrical properties of a semiconductor material. The Q value is a main parameter for measuring inductive devices, and refers to the ratio of the inductive reactance to the equivalent loss resistance of the inductor when the inductor works under an alternating voltage at a certain frequency.

[0004] Therefore, how to avoid the trailing phenomenon of the IDT metal layer has become one of the technical problems to be solved by those skilled in the art.

[0005] It should be noted that the information disclosed in this background section is only intended to increase the understanding of the overall background of the present application, and should not be regarded as acknowledging or implying in any form that the information constitutes prior art known to those skilled in the art. SUMMARY

[0006] The present application provides a preparation method of an elastic wave device, which comprises the following steps: forming a photoresist structure on a part of the area of a substrate; depositing an IDT metal layer on the substrate and the photoresist structure, the IDT metal layer having an extended foot; disposing a self-alignment layer on the surface of the IDT metal layer, the self-alignment layer not completely covering the extended foot; removing the extended foot and the photoresist structure not covered by the self-alignment layer; and forming a frequency modulation dielectric layer on the IDT metal layer and the substrate.

[0007] The application also provides an elastic wave device, which comprises a substrate, an IDT metal layer, a self-alignment layer and a frequency-modulated dielectric layer.

[0008] The substrate has opposite upper and lower surfaces. The IDT metal layer is located on the upper surface of the substrate. The self-alignment layer covers the upper surface and part of the side surface of the IDT metal layer. The frequency-modulated dielectric layer covers the substrate, the IDT metal layer and the self-alignment layer.

[0009] The application also provides an elastic wave device, which comprises a substrate, an IDT metal layer, a self-alignment layer and a frequency-modulated dielectric layer.

[0010] The application also provides an elastic wave device, which comprises a substrate, an IDT metal layer, a self-alignment layer and a frequency-modulated dielectric layer.

[0011] Other features and advantages of the application will be illustrated in the following description, and some technical features and advantages can be obviously obtained from the description or be known by implementing the application. BRIEF DESCRIPTION OF DRAWINGS

[0012] In order to more clearly illustrate the technical solutions of the embodiments of the application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, some of the drawings in the following description are some embodiments of the application, and other drawings can be obtained by those skilled in the art without creative labor on the basis of these drawings.

[0013] Figure 1 is a structural schematic diagram of an elastic wave device provided by the first embodiment of the application;

[0014] Figure 2 is a partial enlarged schematic diagram of the A area in Figure 1

[0015] Figures 3 to 8 is a structural schematic diagram of the elastic wave device shown in Figure 1

[0016] Figure 9 is a structural schematic diagram of an elastic wave device provided by the second embodiment of the application;

[0017] Figures 10 to 15 is a structural schematic diagram of the elastic wave device shown in Figure 9

[0018] ​​​Figure 16 is a structural diagram of an elastic wave device according to an embodiment of the present application;

[0019] Figure 17 is a schematic plan view showing an electrode structure on a piezoelectric substrate;

[0020] Figure 18 is a schematic diagram of an elastic wave device according to an embodiment of the present application, which is a bulk acoustic wave structure. DETAILED DESCRIPTION

[0021] In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are some but not all of the embodiments of the present application; and the technical features in the different embodiments of the present application described below can be combined with each other as long as there is no conflict. Based on the embodiments of the present application, all other embodiments obtained by a person of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0022] In the description of the present application, it should be understood that the terms "center", "transverse", "upper", "lower", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer" and the like indicate the orientation or positional relationship shown in the drawings based on the orientation or positional relationship shown in the drawings, and are only used to facilitate the description of the present application and simplify the description, and do not indicate or imply that the device or component referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation of the present application. In addition, the terms "first", "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the technical features indicated. Therefore, the features defined as "first", "second" can explicitly or implicitly include one or more of the features. In the description of the present application, unless otherwise specified, the meaning of "a plurality of" is two or more. In addition, the term "comprising" and any variation thereof means "at least including".

[0023] Please refer to Figures 1 to 8 , Figure 1 is a structural diagram of an elastic wave device according to an embodiment of the present application, Figure 2 is Figure 1 is a partial enlarged schematic view of the A region in Figures 3 to 8 is Figure 1The elastic wave device is shown in the structure diagram of each stage in the preparation process. To achieve at least one of the advantages or other advantages, an embodiment of the present application provides an elastic wave device. As shown in the figure, the elastic wave device can at least include a substrate 11, an IDT metal layer 12, a self-alignment layer 14 and a frequency modulation dielectric layer 16.

[0024] The substrate 11 has opposite upper and lower surfaces. The material of the substrate 11 can be lithium tantalate (LT) or lithium niobate (LN), but the present application is not limited thereto, and the material of the substrate 11 can also be other materials with relatively stable crystal structure, such as quartz and the like. In some embodiments, the substrate 11 can also include a multilayer structure stacked with a piezoelectric layer, such as sapphire, silicon, aluminum oxide, spinel, quartz or glass.

[0025] The IDT metal layer 12 is located on the upper surface of the substrate 11. IDT (Inter Digital Transducer) is a interdigital transducer. By adding a high-frequency electrical signal to the IDT metal layer 12 through the wiring pattern from the lead terminal on the power side, the surface of the substrate 11 will produce mechanical vibration and at the same time excite surface acoustic waves with the same frequency as the applied electrical signal. The surface acoustic wave will propagate along the surface of the substrate 11. The number of IDT metal layers 12 can be multiple, and multiple IDT metal layers 12 are arranged at intervals on the substrate 11, and the number, position and spacing of the IDT metal layer 12 can be adjusted according to actual needs. The material of the IDT metal layer 12 can include Ti, Al, Cu, Au and the like.

[0026] The self-alignment layer 14 covers the upper surface and part of the side surface of the IDT metal layer 12. By providing the self-alignment layer 14, most of the extended feet 122 of the IDT metal layer 12 in the traditional preparation can be removed, so that the elastic wave device has better K value and Q value, thereby obtaining better product characteristics. The material of the self-alignment layer 14 is different from that of the IDT metal layer 12, so that in the preparation process, the extended feet 122 not covered by the self-alignment layer 14 are removed by means of process. In some embodiments, the self-alignment layer 14 can be an oxide layer. The material of the self-alignment layer 14 can include at least one selected from the group consisting of silicon oxide, silicon nitride, polyethylene and polysilicon. For example: SiO2, Si x N y , Poly, Si x O y and the like. However, the present application is not limited thereto, and the self-alignment layer 14 can also be a metal layer, and the atomic weight of the metal of the self-alignment layer 14 is greater than that of the IDT metal layer 12. The material of the self-alignment layer 14 can include at least one selected from the group consisting of Au, Cu, Cr and Ni. In some embodiments, the thickness S1 of the self-alignment layer 14 can range from 5 to 100 nm.

[0027] The tuning dielectric layer 16 covers the substrate 11, the IDT metal layer 12 and the self-alignment layer 14. By adjusting the covering thickness of the tuning dielectric layer 16, on one hand, the frequency of the elastic wave device can be changed to reach the target frequency, and on the other hand, the IDT metal layer can be covered to be protected. In some embodiments, the material of the tuning dielectric layer 16 can include SiO2.

[0028] The IDT metal layer 12 has an upper width and a lower width, and the lower width of the IDT metal is the line width of the IDT metal. When the difference between the line width and the upper width is too large, the performance of the elastic wave device will be affected. For example, when the longitudinal section of the IDT metal layer 12 is rectangular, the performance of the elastic wave device is better. However, due to the limitation of the process conditions, the longitudinal section of the IDT metal layer 12 usually presents a trapezoidal shape as shown in the figure. In this case, the lower width of the IDT metal layer 12 needs to be as close to the upper width as possible to effectively improve the performance of the elastic wave device. However, the IDT metal layer 12 prepared by the traditional preparation method will form a long extension foot 122 as shown in the figure, which will cause the lower width of the IDT metal layer 12 to be too large, and thus reduce the K value and Q value of the elastic wave device. To solve this problem, the self-alignment layer 14 is added in the embodiment to remove the extension foot 122 that is not covered by the self-alignment layer 14, so as to reduce the lower width of the IDT metal layer 12 and improve the performance of the elastic wave device. In some embodiments, the ratio of the upper width of the IDT metal layer 12 to the lower width thereof can be in the range of 0.75:1 to 1:1, for example, 0.9:1. Figure 6

[0029] In some embodiments, the sidewall of the IDT metal layer 12 along the direction from the lower surface to the upper surface of the substrate 11 (i.e. the direction from bottom to top in the figure) includes a first sidewall 21, a second sidewall 22 and a third sidewall 23 in sequence. The first sidewall 21 protrudes from the third sidewall 23, that is, the first sidewall 21 is more inclined to the outside than the third sidewall 23. The self-alignment layer 14 covers at least the third sidewall 23. Optionally, the self-alignment layer 14 can cover the second sidewall 22. To further effectively remove the too long extension foot 122 of the IDT metal layer 12, the height H1 of the first sidewall 21 can be in the range of 5-100 nm. That is, the height of the sidewall of the IDT metal layer 12 that is not covered by the self-alignment layer 14 is in the range of 5-100 nm. The height refers to the vertical distance from the upper end point of the sidewall to the upper surface of the substrate 11. It should be noted that the right figure and the left figure in the figure are the same structure, and the right figure is intended to show the labeling of the dimensions and angles. Figure 2

[0030] ​​In some embodiments, the angle B between the first sidewall 21 and the horizontal plane and the angle between the third sidewall 23 and the horizontal plane are both greater than the angle between the second sidewall 22 and the horizontal plane. For clarity, only the angle B between the first sidewall 21 and the horizontal plane is shown in the figure; the other angles can be understood by referring to this annotation. In the figure, the angles B between the first sidewall 21 and the horizontal plane, the second sidewall 22 and the horizontal plane, and the third sidewall 23 and the horizontal plane are approximately 80°, 30°, and 78°, respectively.

[0031] like Figures 3 to 8 As shown, the following discloses a method for making Figure 1 The method for the elastic wave device shown.

[0032] First, such as Figure 3 As shown, a photoresist structure 18 is formed in a portion of the substrate 11. The photoresist structure 18 in the figure is a double-layer structure. Specifically, the photolithography process can be performed using the traditional bi-layer method to form this photoresist structure 18. The upper photoresist layer is wider, and the lower photoresist layer is partially undercut.

[0033] Secondly, such as Figure 4 As shown, an IDT metal layer 12 is deposited on the substrate 11 and the photoresist structure 18, and the IDT metal layer 12 formed at this time has extended leads 122. Specifically, an evaporation process can be used to deposit the entire IDT metal onto the substrate 11 and the photoresist structure 18 to form the IDT metal layer 12. As shown in the enlarged view in the figure, during the evaporation process, the IDT metal layer 12 will inevitably generate relatively long extended leads 122.

[0034] Then, as Figure 5 As shown, a self-alignment layer 14 is formed on the surface of the IDT metal layer 12, and the self-alignment layer 14 does not completely cover the extension foot 122. This self-alignment layer 14 can be a thin oxide layer formed by low-temperature sputtering, or a thin non-IDT metal layer formed by vapor deposition. The thickness S1 of the self-alignment layer 14 can be 5–100 nm. Non-IDT metal refers to a metal with a different material than the IDT metal layer 12, and whose atomic weight is greater than that of the metal in the IDT metal layer 12. Because the self-alignment layer 14 of the non-IDT metal is thin, the diffusion time is very short, and the extension foot 122, which is the same length as the IDT metal layer 12, will not form on the surface of the IDT metal layer 12.

[0035] Next, as Figure 6 As shown, the photoresist structure 18 and the IDT metal layer 12 on the photoresist structure 18 can be removed first. Specifically, this can be achieved by using a conventional lift-off process to remove the metal.

[0036] Then, asFigure 7 As shown, the extension pins 122 not covered by the self-alignment layer 14 are removed to improve the performance of the elastic wave device. Specifically, depending on the material of the self-alignment layer 14, different methods can be used to move the extension pins 122. For example, when the self-alignment layer 14 is a non-IDT metal layer, such as Cu, and the IDT metal layer 12 is Al, since Cu has a relatively large atomic weight, a dry etching process with a high selectivity of Al:Cu is used to process the Al film using a Descum process. The extension pins 122 not covered by the Cu film will then be completely removed, thus achieving self-aligned etching. When the self-alignment layer 14 is an oxide layer, the introduced gas can be controlled to react only with the metal extension pins 122 and not with the oxide layer, thereby removing the extension pins 122 not covered by the oxide layer and achieving the purpose of removing the extension pins 122.

[0037] Finally, as Figure 8 As shown, a frequency-modulated dielectric layer 16 is formed on the IDT metal layer 12 and the substrate 11. Specifically, conventional processes can be used; after frequency testing, the SiO2 film for frequency modulation is directly formed according to actual needs to form the frequency-modulated dielectric layer 16. In some embodiments, a SiO2 film of a certain thickness can be formed first, and then the thickness of the SiO2 film can be adjusted according to the frequency to achieve a frequency correction effect.

[0038] Please see Figures 9 to 15 , Figure 9 This is a schematic diagram of the elastic wave device provided in the second embodiment of the present invention. Figures 10 to 15 yes Figure 9 The diagram shows the structural schematics of the elastic wave device at each stage of its fabrication process. Compared to... Figure 1 The main difference between this embodiment and the elastic wave device shown is that the elastic wave device further includes an anti-reflection layer 20, which is located between the IDT metal layer 12 and the substrate 11. The function of the anti-reflection layer 20 is to reduce the standing wave effect and improve the uniformity of light reflection by utilizing light absorption. The material of the anti-reflection layer 20 can include metallic materials. The material of the anti-reflection layer 20 can include materials such as Ti, TlN, Cr, and Ni.

[0039] like Figures 10 to 15 As shown below, a method for making Figure 9 The method for the elastic wave device shown.

[0040] First, such as Figure 10 As shown, an anti-reflective layer 20 covering the entire surface is formed on the substrate 11. Then, a photoresist structure 18 is formed in a portion of the anti-reflective layer 20. The photoresist structure 18 can be a double-layer structure, a single-layer structure, etc. Specifically, the photoresist structure 18 can be formed by performing a photolithography process using the traditional bi-layer method.

[0041] Secondly, such as Figure 11 As shown, an IDT metal layer 12 is deposited on the substrate 11 and the photoresist structure 18, and the IDT metal layer 12 formed has extended leads 122. Specifically, an evaporation process can be used to deposit the entire IDT metal onto the substrate 11 and the photoresist structure 18 to form the IDT metal layer 12. During the evaporation process, the IDT metal layer 12 will inevitably have relatively long extended leads 122.

[0042] Then, as Figure 12 As shown, a self-alignment layer 14 is formed on the surface of the IDT metal layer 12, and the self-alignment layer 14 does not completely cover the extension lead 122. This self-alignment layer 14 can be formed as a thin oxide layer using low-temperature sputtering, or it can be formed as a thin non-IDT metal layer using vapor deposition. The non-IDT metal refers to a metal with a different material than the IDT metal layer 12, and whose atomic weight is greater than that of the metal in the IDT metal layer 12. Because the non-IDT metal self-alignment layer 14 is thin, the diffusion time is very short, and the extension lead 122, which is the same length as the IDT metal layer 12, will not form on the surface of the IDT metal layer 12.

[0043] Next, as Figure 13 As shown, the photoresist structure 18 and the IDT metal layer 12 on the photoresist structure 18 can be removed first. Specifically, this can be achieved by using a conventional lift-off process to remove the metal. During the removal process, the anti-reflective layer 20 located under the photoresist structure 18 will also be removed.

[0044] Then, as Figure 14 As shown, the extension pins 122 not covered by the self-alignment layer 14 are removed to improve the performance of the elastic wave device. During this process, the anti-reflection layer 20 located beneath the extension pins 122 not covered by the self-alignment layer 14 is also removed. Specifically, depending on the material of the self-alignment layer 14, different methods can be used to move the extension pins 122. For example, when the self-alignment layer 14 is a non-IDT metal layer, such as Cu, and the IDT metal layer 12 is Al, since Cu has a relatively large atomic weight, a dry etching process with a high selectivity of Al:Cu is used to process the Al film using a descum process. The extension pins 122 not covered by the Cu film will then be completely removed, thus achieving self-aligned etching. When the self-alignment layer 14 is an oxide layer, the introduced gas can be controlled to react only with the metal extension pins 122 and not with the oxide layer, thereby removing the extension pins 122 not covered by the oxide layer and achieving the purpose of removing the extension pins 122.

[0045] Finally, as Figure 15As shown, the frequency-modulating dielectric layer 16 is formed on the IDT metal layer 12 and the substrate 11. The frequency-modulating dielectric layer 16 can be formed by using a conventional process, and a SiO2 film is plated directly according to the actual needs after the test frequency.

[0046] Please refer to Figure 16 and Figure 17 , Figure 16 is a structural schematic diagram of an elastic wave device provided by an embodiment of the present application, Figure 17 is a schematic top view showing the electrode structure on the piezoelectric substrate 1; in Figure 17 , the structure of the side wall portion 7, the cover 8 and the external connection portion 9 in Figure 16 is schematically removed in the top view. As shown in Figure 16 , the elastic wave device comprises the piezoelectric substrate 1, the elastic wave component 2, the side wall portion 7, the cover 8 and the external connection portion 9.

[0047] The piezoelectric substrate 1 is made of a piezoelectric single crystal such as lithium tantalate, lithium niobate or crystal, or can also be made of a piezoelectric ceramic. In some embodiments, the piezoelectric substrate 1 can also be bonded to a circuit substrate 10 made of, for example, a sapphire substrate, an alumina substrate, a spinel substrate or a silicon substrate. In particular, the piezoelectric substrate 1 comprises a first surface provided with the elastic wave component 2 and a second surface opposite to the first surface, which can be used to bond the circuit substrate 10.

[0048] The elastic wave component 2 is arranged on the first surface of the piezoelectric substrate 1. A self-alignment layer 14 is arranged on the surface of the elastic wave component 2 to remove the extended feet of most of the elastic wave component 2, so as to avoid the occurrence of a tailing condition, and thus the prepared elastic wave device has excellent product characteristics. A frequency-modulating dielectric layer 16 is arranged on the piezoelectric substrate 1, and the frequency-modulating dielectric layer 16 also covers the elastic wave component 2 and the self-alignment layer 14.

[0049] In fact, the elastic wave component 2 has a plurality of resonators 2a, thereby constituting an elastic wave filter. More specifically, the resonators 2a comprise interdigital electrodes (or Interdigital Transducers, IDT for short) 2a for exciting elastic surface waves and reflectors 2b formed on the piezoelectric substrate 1. The interdigital electrodes 2a comprise a pair of oppositely arranged comb electrodes 2c. The comb electrodes 2c each have a plurality of electrode fingers 2d and bus bars 2e connected to the electrode fingers 2d. The reflectors 2b are arranged on both sides of the interdigital electrodes 2a.

[0050] The first wiring 3 and the second wiring 4 are made of a suitable metal or alloy such as silver, aluminum, copper, titanium, palladium, etc.

[0051] The side wall portion 7 surrounds the elastic wave component 2. The side wall portion 7 is made of synthetic resin. Preferably, the side wall portion 7 is made of photosensitive resin. The photosensitive resin is easy to obtain a pattern by photolithography. Thereby, it is easy to obtain an opening portion for forming a space not to interfere with the vibration of the elastic wave component 2, or a through hole for arranging the wiring of the external connection portion 9. The photosensitive resin can use photosensitive polyimide, photosensitive epoxy resin, photosensitive silicone, etc. Preferably, in order to achieve accurate patterning, photosensitive polyimide can be used, but is not limited thereto.

[0052] The cover 8 cooperates with the side wall portion 7 to form and seal the elastic wave component 2 in a manner not to interfere with the vibration of the elastic wave component 2, thereby constituting a sealed cavity so that the elastic wave component 2 can work normally. The cover 8 can be made of synthetic resin, and the synthetic resin constituting the cover 8 can use epoxy resin or polyimide, but is not limited thereto. Preferably, epoxy resin can be used, and the cover 8 is formed by a low-temperature hardening process.

[0053] The elastic wave component 2 is formed on the piezoelectric substrate 1 with the first wiring 3 and the second wiring 4. The elastic wave component 2 can appropriately adopt a DMS structure design and a ladder design in order to obtain a desired bandpass filter characteristic. The wiring constituting the input terminal In, the output terminal Out, and the ground terminal GND is formed by part of the first wiring 3 and part of the second wiring 4, and the elastic wave component 2 is electrically connected to the input terminal In, the output terminal Out, and the ground terminal GND through the first wiring 3.

[0054] Please refer to Figure 18 , Figure 18 is a schematic diagram of an elastic wave device according to an embodiment of the present application. As shown in the diagram, the elastic wave device can be a bulk acoustic wave structure. The thickness of the piezoelectric layer 50 is not particularly limited, but is preferably 50 nm or more and 1000 nm or less in order to effectively excite a thickness shear first-order mode. The piezoelectric layer 50 has an upper surface and a lower surface that face each other in a vertical direction. An electrode finger 53 and an electrode finger 54 are provided on the upper surface. The electrode finger 53 and the electrode finger 54 are covered with a self-alignment layer 14 to remove most of the extended legs of the electrode finger 53 and the electrode finger 54, thereby avoiding a tailing situation and allowing the elastic wave device to have excellent product characteristics. A frequency-modulated dielectric layer 16 is provided on the piezoelectric layer 50, and the frequency-modulated dielectric layer 16 also covers the electrode finger 53, the electrode finger 54, and the self-alignment layer 14.

[0055] On the lower surface side of the piezoelectric layer 50, a support substrate 58 is layered via a dielectric film 57. The dielectric film 57 and the support substrate 58 have a frame-like shape and have opening portions 57a, 58a, respectively. Thus, a hollow portion 59 (air gap) is formed.

[0056] The hollow portion 59 is provided so as not to interfere with the vibration of the excitation region of the piezoelectric layer 50. Therefore, the support substrate 58 described above is layered on the lower surface via the dielectric film 57 at a position not overlapping with the portion in which at least one pair of the electrode fingers 53, 54 is provided. Alternatively, the dielectric film 57 can not be provided. Therefore, the support substrate 58 can be layered on the lower surface of the piezoelectric layer 50 directly or indirectly.

[0057] The dielectric film 57 is formed of silicon oxide. However, the dielectric film 57 can be formed of silicon nitride, alumina, or the like, in addition to silicon oxide.

[0058] The support substrate 58 is formed of Si. Preferably, Si having a high resistance of 4 kΩ or more is appropriate. However, the support substrate 58 can be configured using an appropriate insulating material or a semiconductor material. As the material of the support substrate 58, for example, a piezoelectric body such as alumina, lithium tantalate, lithium niobate, quartz, alumina, magnesia, sapphire, silicon nitride, aluminum nitride, silicon carbide, zirconia, cordierite, mullite, block talc, forsterite, various ceramics, a dielectric such as diamond, glass, a semiconductor such as gallium nitride, or the like can be used.

[0059] The plurality of electrode fingers 53, 54 described above can contain an appropriate metal or alloy such as Al or an AlCu alloy. The electrode fingers 53, 54 have a configuration in which an Al film is layered on a Ti film. Alternatively, a tight layer other than the Ti film can be used.

[0060] During driving, an alternating voltage is applied between the plurality of electrode fingers 53 and the plurality of electrode fingers 54. More specifically, an alternating voltage is applied between the two bus bar electrodes. Thus, a resonance characteristic using a bulk wave of a thickness shear first mode excited in the piezoelectric layer 50 can be obtained.

[0061] An embodiment of the present application also provides an elastic wave device including an elastic wave device and a circuit substrate. The elastic wave device is provided on the circuit substrate, and the elastic wave device can employ the elastic wave device described above.

[0062] In summary, an embodiment of the present application provides an elastic wave device, an elastic wave device, and a method for manufacturing the same. By providing a self-alignment layer 14, most of the footings 122 of the IDT metal layer 12 can be effectively removed, and tailing can be avoided. Thus, the elastic wave device has excellent product characteristics.

[0063] In addition, those skilled in the art should understand that, although there are many problems in the prior art, each embodiment or technical solution of the present application can only be improved in one or several aspects, and it is not necessary to solve all the technical problems listed in the prior art or background art at the same time. Those skilled in the art should understand that what is not mentioned in a claim should not be regarded as a limitation of the claim.

[0064] Finally, it should be pointed out that the above embodiments are only used to illustrate the technical solutions of the present application, and not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement for part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A method of fabricating an elastic wave device, characterized by: The method for manufacturing the elastic wave device comprises the following steps: forming a photoresist structure on a part of the substrate; depositing an IDT metal layer on the substrate and the photoresist structure, the IDT metal layer having an extended leg; providing a self-alignment layer on the surface of the IDT metal layer, the self-alignment layer not completely covering the extended leg; the material of the self-alignment layer is different from the material of the IDT metal layer; removing the extended leg and the photoresist structure not covered by the self-alignment layer; forming a frequency-modulating dielectric layer on the IDT metal layer and the substrate.

2. The method of manufacturing an elastic wave device according to claim 1, wherein: The self-alignment layer is an oxidation layer.

3. The method of manufacturing an elastic wave device according to claim 1 or 2, characterized in that: The material of the self-alignment layer comprises at least one selected from the group consisting of silicon oxide, silicon nitride and polyethylene.

4. The method of manufacturing an elastic wave device according to claim 1, wherein: The self-alignment layer is a metal layer, the atomic weight of the metal of the self-alignment layer is greater than the atomic weight of the metal of the IDT metal layer.

5. The method of manufacturing an elastic wave device according to claim 1 or 4, wherein: The material of the self-alignment layer comprises at least one selected from the group consisting of Au, Cu, Cr and Ni.

6. The method of manufacturing an elastic wave device according to claim 1, wherein: The material of the frequency-modulating dielectric layer comprises SiO2.

7. The method of manufacturing an elastic wave device according to claim 1, wherein: The method further comprises the following step before the step of forming the photoresist structure: providing an anti-reflection layer on the substrate, the material of the anti-reflection layer comprising a metal material.

8. The method of manufacturing an elastic wave device according to claim 1, wherein: The process of removing the extended leg is a dry etching process.

9. An elastic wave device characterized by: The elastic wave device comprises: a substrate having opposite upper and lower surfaces; an IDT metal layer on the upper surface of the substrate; a self-alignment layer covering the upper surface and part of the side surface of the IDT metal layer; a frequency-modulating dielectric layer covering the substrate, the IDT metal layer and the self-alignment layer; wherein the side wall of the IDT metal layer comprises a first side wall, a second side wall and a third side wall in sequence along the direction from the lower surface to the upper surface of the substrate, the first side wall protruding from the third side wall, and the self-alignment layer covering at least the third side wall.

10. The elastic wave device of claim 9, wherein: The IDT metal layer has an upper width and a lower width, and the ratio of the upper width to the lower width ranges from 0.75:1 to 1:

1.

11. The elastic wave device of claim 9, wherein: The ratio of the sum of the lengths of the first side wall and the second side wall to the length of the third side wall ranges from 1:1 to 1.3:

1.

12. The elastic wave device of claim 11, wherein: The self-alignment layer covers the second side wall.

13. The elastic wave device of claim 11, wherein: The included angle between the first side wall and the horizontal plane and the included angle between the third side wall and the horizontal plane are greater than the included angle between the second side wall and the horizontal plane.

14. The elastic wave device of claim 9, wherein: The material of the self-alignment layer is different from the material of the IDT metal layer.

15. The elastic wave device of claim 9, wherein: The self-alignment layer is an oxidation layer.

16. The elastic wave device of claim 9 or 15, wherein: The material of the self-alignment layer comprises at least one selected from the group consisting of silicon oxide, silicon nitride and polyethylene.

17. The elastic wave device of claim 9, wherein: The self-alignment layer is a metal layer, the atomic weight of the metal of the self-alignment layer is greater than the atomic weight of the metal of the IDT metal layer.

18. The elastic wave device of claim 9 or 17, wherein: The material of the self-alignment layer comprises at least one selected from the group consisting of Au, Cu, Cr and Ni.

19. The elastic wave device of claim 9, wherein: The thickness of the self-alignment layer ranges from 5 to 100 nm.

20. The elastic wave device of claim 9, wherein: The elastic wave device further comprises an anti-reflection layer between the IDT metal layer and the substrate.

21. An elastic wave device characterized by comprising: The elastic wave device includes an elastic wave device and a circuit substrate, the elastic wave device is provided on the circuit substrate, and the elastic wave device is the elastic wave device according to any one of claims 9 to 20. The elastic wave device includes an elastic wave device and a circuit substrate, the elastic wave device is provided on the circuit substrate, and the elastic wave device is the elastic wave device according to any one of claims 9 to 20.

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